The invention relates to medical devices for intermittently pulsed compression of a part of the human body, specifically for intermittent compression at or near a joint, such as a knee, an elbow or a shoulder, in treatment of a painful disorder of tissue circulation at or near the joint.
It is known from U.S. Pat. No. 4,614,180 that impulse compression, locally applied as intermittent pressure pulses in the plantar region of the foot, is an effective means of enhancing venous-return of blood to the heart. This technique is an artificial substitute for the action of weight-bearing, in alternation between one foot and the other, in the course of walking, for a healthy person, by reason of body weight flattening the plantar arch, i.e., transiently spreading the ball and heel of the foot slightly apart, with concomitant stretching and necking-down of the veins in the plantar region. For the patient who is unable to walk and who may have a thrombotic condition with accompanying pain, the artificially induced intermittent compression of the plantar region has been found to provide the patient with a highly effective means of assuring venous return, of such therapeutic value as to bring welcome relief from pain, as well as to reduce swelling and, in many cases, to eliminate the thrombotic condition. U.S. Pat. No. 4,721,101 describes an extension of the same concept, with slight modification, indicating that such action on the plantar veins can also be effective in enhancement of arterial flow in the involved limb.
Impulse compression devices of the character indicated rely on the facts (i) that veins of the plantar complex provide a reservoir of accumulated and accumulating blood, and (ii) that the venous system is characterized by check valves to assure against back flow of blood that must be returned to the heart in the course of healthy circulation. The reservoir veins are squeezed to force blood return via the one-way return system of check valves, for each compressional action on the plantar veins. A suitable inactive period of about 20 seconds allows the plantar veins to swell with a new charge of blood, to be returned by the next compressive actuation at the plantar region.